Two soap formulations, both containing 20% deet and one each containing permethrin at 0.5 and 1.0%, respectively, were applied to exposed arms and legs of volunteers as personal protection against outdoor human biting mosquitoes in six locations on Penang Island, Malaysia. The predominant mosquito species collected from these locations were Aedes albopictus, Mansonia uniformis, Culex gelidus, Anopheles lesteri and Armigeres subalbatus. Efficacy and residual effects up to 4 hours indicated good protection against these species. Reduction in mosquito landing-biting rates in treated groups ranged from 83.8 to 100.0%. At high densities, small percentages of Ma. uniformis and An. lesteri landed or bit on treated skin. Use of the soap formulations in terms of cost-effectiveness, safety and overall vector control strategy for some tropical diseases is discussed.
Matched MeSH terms: Insect Bites and Stings/prevention & control
Two new repellent formulations, KBR 3023 10% and 20% from Bayer AG, Germany, were evaluated together with DEET 10% and 20% as standard repellent formulations. Evaluation was based on two separate field studies: a daytime study (0900-1700 hr) in a forested orchard on Penang Island and a nighttime study (2100-0100 hr) in a squatter residential area on the adjacent mainland of peninsular Malaysia. Both studies were carried out by exposing humans with bare arms and legs to mosquitoes landing/biting for an eight hour period. Right arms and legs of the human baits were treated with different repellent formulations (KBR 3023 10%, 20% and DEET 10%, 20%) and the left limbs were left untreated to act as controls. The daytime study indicated that all four formulations were equally effective (P < 0.05) as repellents against the predominant Aedes albopictus with greater than 88.5% reduction in landing/biting in the first four hours and not less than 65.0% in the next four hours of the assessment period. In the night study, all four formulations were also found to be equally effective (P < 0.05) in repelling Culex quinquefasciatus, the predominant species. All four formulations provided complete protection against Cx. quinquefasciatus in the first two hours of exposure. The percentage reduction values were maintained above 90.0% for the next six hours of the assessment period. In conclusion, both the KBR 3023 and DEET formulations were found to be equally effective (P < 0.05) in providing a long-lasting reduction in human-mosquito contact in both the day and night field studies.
Matched MeSH terms: Insect Bites and Stings/prevention & control*
Two field trials in the control of subperiodic brugian filariasis vectors, mainly Mansonia bonneae and Mansonia dives were carried out in Sarawak, East Malaysia. In the first trial, malathion ultra-low volume (ULV) spray was used to control the Mansonia mosquitos in two filariasis endemic villages. Six spray rounds were applied at biweekly intervals at Kampung Rasau and two spray rounds were applied at monthly intervals in Kampung Triboh. ULV malathion spray reduced biting Ma. bonneae population for 3 days after spraying. The biting density decreased to 50% of the pre-treatment level by the 12th - 13th day and reached the pre-treatment level by the 24th - 25th day. Contact bioassay tests on caged Mansonia mosquitos revealed considerable penetration of the malathion aerosol indoors and relatively adequate coverage outdoors. The estimated number of bites per case per day was 1.09 to 4 times less in the sprayed kampung than in an unsprayed control kampung. The parous and daily survival rates of Mansonia mosquitos were not significantly affected by the spraying. In a second trial, chemotherapy with diethylcarbamazine citrate (DEC) was combined with vector control through indoor residual spraying in Kampung Ampungan. The results were compared with the use of only DEC mass treatment in Kampung Sebangkoi and Kampung Sebamban. The combined control measures in Kampung Ampungan reduced the MfD-50 to 44% of the pre-treatment level over a period of 4 years. In the other two kampungs where only mass DEC therapy was applied, the microfilarial rate and MfD-50 declined significantly in the second blood survey but increased gradually in two subsequent follow-up blood surveys. The total insecticidal impact for Ma. bonneae was 3.9 to 1 indoors and 2.7 to 1 outdoors. These results indicated that quarterly pirimiphos-methyl indoor spraying used in integrated control could reduce indoor transmission by 3.9 times. The infective rate from the Ma. bonneae dissected in all three kampungs after the interventions, irrespective of DEC treatment alone or in combination with pirimiphos-methyl residual spraying were reduced by two fold. However the infection rate of brugian filarial larvae in Kampung Ampungan was significantly reduced after the use of DEC and insecticide. Annual Transmission Potential (ATP) showed a high significant reduction in Kampung Ampungan (p > 0.001) compared with Kampungs Sebangkoi and Schambam. In Ampungan, the ATP was reduced by 8.5 times indoors after the MDA and insecticidal application and 3 times outdoors. The reduction rate for Sebangkoi and Sebamban both indoors and outdoors were less than 2 fold.(ABSTRACT TRUNCATED AT 400 WORDS)
Matched MeSH terms: Insect Bites and Stings/prevention & control
BACKGROUND & OBJECTIVES: Many essential oils have been reported as natural sources of insect repellents; however, due to high volatility, they present low repellent effect. Formulation technique by using microencapsulation enables to control the volatility of essential oil and thereby extends the duration of repellency. In this study, the effectiveness of microencapsulated essential oils of Alpinia galanga, Citrus grandis and C. aurantifolia in the lotion formulations were evaluated against mosquito bites.
METHODS: Essential oils and N,N-Diethyl-3-methylbenzamide (DEET) were encapsulated by using interfacial pre- cipitation techniques before incorporation into lotion base to form microencapsulated (ME) formulation. The pure essential oil and DEET were also prepared into lotion base to produce non-encapsulated (NE) formulation. All the prepared formulations were assessed for their repellent activity against Culex quinquefasciatus under laboratory condition. Field evaluations also were conducted in three different study sites in Peninsular Malaysia. In addi- tion, Citriodiol® (Mosiquard®) and citronella-based repellents (KAPS®, MozAway® and BioZ Natural®) were also included for comparison.
RESULTS: In laboratory conditions, the ME formulations of the essential oils showed no significant difference with regard to the duration of repellent effect compared to the microencapsulated DEET used at the highest con- centration (20%). It exhibited >98% repellent effect for duration of 4 h (p = 0.06). In the field conditions, these formulations demonstrated comparable repellent effect (100% for a duration of 3 h) to Citriodiol® based repellent (Mosiguard®) (p = 0.07). In both test conditions, the ME formulations of the essential oils presented longer duration of 100% repellent effect (between 1 and 2 h) compared to NE formulations.
INTERPRETATION & CONCLUSION: The findings of the study demonstrate that the application of the microencapsulation technique during the preparation of the formulations significantly increases the duration of the repellent effect of the essential oils, suggesting that the ME formulation of essential oils have potential to be commercialized as an alternative plant-based repellent in the market against the mosquitoes.
Matched MeSH terms: Insect Bites and Stings/prevention & control*
A study was conducted to determine the incidence of trypanosome infections in cattle in tsetse-free and tsetse-infested zones of the Amhara Region of northwest Ethiopia. A total of six sentinel herds were established and the cattle observed during a period of 8 consecutive months. The prevalence of seropositive cattle was high in both the tsetse-free and tsetse-infested zones. The average monthly incidence of trypanosome infection, determined using molecular diagnostic tools, was 20.9% and 25.7% in the tsetse-free and the tsetse-infested zones, respectively. In the tsetse-free, Trypanosoma vivax was responsible for 90.9% of the cattle trypanosome infections. In the tsetse-infested zone, Trypanosoma congolense and T. vivax contributed almost equally to the trypanosome infections in cattle. Trypanosome infection, regardless of species, resulted in anaemia as evidenced by a significant decrease in the packed cell volume of the infected animal. The outcome of this longitudinal study suggests that control of trypanosomiasis in the Amhara Region cannot be achieved by tsetse control alone. Supplemental measures to include drug therapy and biting fly control are discussed.
Matched MeSH terms: Insect Bites and Stings/prevention & control
A control programme against subperiodic brugian filariasis was implemented in three villages, (Kg. Ampungan, Kg. Sebangkoi and Kg. Sebamban) in Sarawak, Malaysia. In Kampong Ampungan, the mass administration of diethylcarbamazine (DEC-citrate) combined with residual house spraying of pirimiphos-methyl reduced microfilarial rate to 8% of the pre-treatment level and microfilarial density (MfD50) to 44% of the pre-treatment level over a period of four years. In Kampong Sebangkoi and Kampong Sebamban, where only mass DEC therapy was applied, the microfilarial rate and MfD50 declined distinctly in the second blood survey but increased gradually in two subsequent follow-up blood surveys. In Kg, Ampungan, we observed a significant reduction of infective biting rate (88.3%), infection rate (62.5%) and transmission potential (88.1%) of Mansonia bonneae at the fourth spray round. The corresponding reduction rates in Kg. Sebangkoi and Kg. Sebamban were 35.3%, 26.7%, 42.2% and 24%, 30.8% and 15.4% respectively. The biting density of the vector was reduced by 79.8% indoors and 31.8% outdoors at the sprayed village, while only a slight decrease in densities (17.9% indoors and 12.4% outdoors) was observed at the unsprayed village. Bioassay tests revealed that pirimiphos-methyl had a substantial fumigant effect on the vector. The integrated control measure in controlling subperiodic brugian filariasis is discussed.
Matched MeSH terms: Insect Bites and Stings/prevention & control